1. Field of the Invention
The invention relates generally to connecting devices such as sensors or actuators to an electronic interconnecting apparatus. The invention relates specifically to an interconnect device having an efficient means for detecting and breaking short circuits in an actuatable device with minimal usage of pins from a microcontroller contained within the interconnect device.
2. Description of the Related Art
Commercial bus devices for industrial usage such as SMART DISTRIBUTED SYSTEM.TM. by Honeywell Inc. are made for large scale material handling or the like. These bus systems comprise 4-wire buses with two wires for power and 2 wires for communication and control. The bus may operate, for example, a conveyor line having a plurality of sensors for sensing packages and/or a plurality of actuators such as, for example, controllable routers for routing the packages onto and off the conveyor. The sensors and actuators, hereinafter referred to simply as "devices", are often connected to the main bus lines by means of bus interconnect apparatus. These interconnect apparatus can handle a plurality of connections between the main bus line and the devices. The interconnect apparatus can contain microcontrollers for timing and routing signals to the devices. Alternatively, the devices themselves may contain the microcontroller to enable a variety of features such as counting, operator interface enablement, or the like.
It will be appreciated that the devices under discussion need not be connected to a bus, per se. They could for example be stand alone devices, or grouped devices, operating without the benefit of a full communications bus architecture. Therefore the term "bus" as used herein is better thought of in its broadest sense as a "communications or data line" which enables a sensing and control assemblage, or network, to communicate the data produced by the sensor or which carries the actuation pulses to the actuators.
In order to keep the cost of the devices or their interconnect apparatus low, while maximizing the features, great efficiency should be exercised in the use of the pin assignments on the microcontroller to enable the use of the least expensive microcontroller for the tasks at hand.
In the case where a device short circuits, it is desirable that the device be turned off as rapidly as possible in order to avoid damage to any of the components in the devices or interconnect apparatus, and also eliminate power drains, incorrect information, or false actuations.
In the past, short circuit sensing and control mechanisms have less efficiently utilized the microcontroller contained within the interconnect device. However, as previously stated, it is desirable to utilize the least amount of microcontroller pins in order to achieve such functionality. Further, a typical prior device would utilize an interrupt detection method which slows reaction time to short circuit conditions, as well as consuming valuable microcontroller resources in the form of software interrupts to the I/O pins of the microcontroller.
Therefore, it is desirable to have a means for more immediately detecting and shutting down short circuited sensing and control network devices while utilizing the least number of microcontroller pins.